Insulating composition



(No Model.)

THOMSON. INSULATING (JGMPOSITION;

Patented Nov. '14

L E F WITNESSES- ms NATIONAL umcqmmme ccMPANv.

WASHINGYON. n4 0.

ELIHU THOMSON, OF SWAMPSCOTT,

:PATENT OFFICE.

MASSACHUSETTS, ASSIGNOR TO THE THOMSON-HOUSTON ELECTRIC COMPANY, OFCONNECTICUT.

INSULATING COMPOSITION.

SPECIFICATION forming part of Letters Patent No. 508,653, dated November14, 1893.

Application find November 2, 1891.

To all whom it may concern.-

Be it known that I, ELIHU THOMSON, a citizen of the United States,residing at-Swampscott, in the county of Essex and State ofMassachusetts,have invented certain new and usefullmprovements inInsulating Compositions, of which the following is a specification.

My present invention relates to the production of slabs of insulatingmaterial suchas are suitable for use in the construction of dynamoelectric machines in place of mica where strength, together with someflexibility is required, and wherethe material must resist the formationof carbonized lines or carbonized paths through the same transverselytothe sheet or slab.

In the accompanying drawings Figure 1 inch in thickness, more or less,)and coat or impregnate the same with a deposit or a thin layer ofmineral substance such as a mixture of fine kaolin or silicious compoundor equivalent thereto and soluble silicate of soda. This may be done byapplying a silicious solution to the paper. I pile these sheets as shownin Fig. 1, into a mass A, which gives a slab of the desired thickness.The silicious material will thus be incorporated more or less with thepaper and may penetrate throughout the same or may be mostly on thesurface,in the form of a coating or layer, which should, however, be asthin as practicable. The mass is then dried out so as to remove allmoisture from it, and then forms thin slabs of insulating material whichare adaptable to many purposes, the strength being conferred by thepaper while the deposit or layers of silicious matter form insulatinglayers which prevent the formation of a carbonized line of particlesacross the same. Hence the compound may be used in commutator insulationbetween the segments or the like. The alternate ar- Serial No 410,603.(No specimens.)

rangement of the paper layers a and the sili cious coatings b isindicated in Fig.2. While the material simply. dried in this manner isadapted for many purposes, I prefer to perfect the substance-by bakingit at a moderate red heat whereby the paper is more or less carbonizedand the silicious matter more or less vitrified or fritted together intoa thin, flexible slab with carbonized paper more or less incorporatedtherewith. In other cases I heat the slab in contact with air for asufficient time to burn out the carbonaceous matter left by the paper.In this latter case however, the strength will not be as great. Bybaking as described, there is obtained a series ofthin slabs ofinsulating material resembling baked porcelain, clay, or half formedglass which may be retained in the form of a slab or split up intolayers, as desired.

I prefer to make the silicious deposit mainly as a coating or externallayer, so as to give distinct silicious layers in the completed article.By burning out the paper completely it is even possible to separate thelayers after baking so as to obtain thin flat sheets of what wouldresemble porcelain. In this case the invention is practiced as follows,the object being to produce a series of thin plates of porcelain biscuitor unglazed porcelain made at a comparatively low temperature. I takethe paper sheets and place between them thin slabs of the clay orsilicate mixture and pile them one above the other,-paper, clay mixture,paper, clay mixture, &c., to any desired thickness. I then thoroughlydry the mass as uniformly as possible so as to avoid warping. It is thenbaked at a moderately high temperature such as a bright red heat and ifdesired the heat continued until the paper being carbonized is burnedout by the presence of oxygen. 1 then haveabundle of thin slabs whichmay be either used as such or by separating them one from the other, asdesired, by splitting them apart. By shaping the coated paper into theproper form, the finished material may be made to take any form desired, for example that indicated in Figs. 3 and 4, and to consist oflayer upon layer of the vitreous substance separated by what remains ofthe paper as carbonized material or as ash according to the degree ofbaking, although my process, as stated before, does not necessarilyinvolve the baking process if the ma terial is not to be waterproof.

Instead of silicious compounds I may use any other materials, of therequisite insulating and non-carbonaceous nature, such for example asearthy oxides or other metallic salts. It is preferred however to employa mixture of silicates, such as an earth silicate, giving a body, and analkaline silicate which serves as a cementing material.

What I claim as new, and desire to secure by Letters Patent, is

1. The process of making insulating material which consists in applyingnon-carbonaceous material to sheets of paper, piling said sheetstogether, and drying the resultingmass.

2. The process of making insulating material which consists in applyingsilicious or equivalent material to sheets of paper, piling said sheetstogether, and drying and baking the resulting mass so as to consolidatethe same.

3. The process of making insulating material which consists in applyingto paper sheets an earthy or mineral substance with a binding material,piling said sheets together and drying and heating the resulting mass.

4. As a new article of manufacture, an insulating material consisting oflayers of carbonaceous material alternating with layers of siliciousmaterial.

5. As a new article of manufacture, an insulating material consisting oflayers of more or less carbonized paper and intervening layers of moreor less vitrified silicious material.

In witness whereof I have hereunto set my hand this 27th day of October,1891.

ELIHU THOMSON.

Witnesses:

JOHN W. GIBBONEY, ALBERT L. ROHRER.

